1. Field of the Invention
The invention relates to inertial rate sensors and more particularly to vibratory rate of turn sensor devices of a type employing force feed back techniques, thereby maintaining motion of a vibratory element in a lineal or nulled path with respect to the sensing axes under turn-induced disturbing forces, a measure of the force feed back being a measure of the disturbing force and hence of the turn rate.
2. Background of the Invention
The present invention is an improvement over the closed-loop vibrating rate sensor disclosed in the above referenced pending application which, in turn, is broadly related to vibrating rate sensors of the general types disclosed in U.S. reissue Pat. No. 22,409, dated Dec. 21, 1943 to J. Lyman and E. Norden, assigned to Sperry Corporation.
As disclosed in the pending application with respect to piezoelectric or piezoceramic devices, operation is based upon electrical-charge mechanical-strain phenomenon in the material, usually referred to as having a coupling coefficient, which phenomenon may be employed to vibrate a mass thereby to develop linear momentum in the mass. In open loop sensors which use the high resolution of this energy conversion mechanism, the drift and scale factor characteristics are dependent upon, among other characteristics, the stability and properties of the piezoelectric material coupling coefficient. Thus, use of piezoelectric devices in inertial instruments has been hampered by drift in stability and scale factor inconsistencies, to be overcome only to a degree in the past by intensive development of relatively stable piezoelectric materials and application thereof in particular sensor designs. These improved materials, when configured in accordance with the present vibrating rate sensor concepts, together with the shape and manner in which the vibratory element and its associated pick-off electrodes and driving elements are arranged relative thereto, provide substantial improvements in the overall operating characteristics of the sensor, including reduced cross-coupling effects between the drive and nulling axes, reduced environmental temperature sensitivity, reduced susceptibility to environmental vibrations, and over-all improvement in sensor scale factor.